For a pretty solid trip in China, based on seeing the major sights, using air or train travel, with private cars and guides, but not factoring jet lag (add a day to arrival city if coming from North America or Europe), I recommend the following as an outline of the major cities to visit:

(in order
of priority)
Min. #
Hotel
Nights
Min. #
Days
Travel
Days
Beijing 3-4 4-5 1
Xi’an
TerraCotta
1 1 2 (in/out)
Shanghai 1-2 2-3 1
Zhouzhuang
Water Town
0 1 drive
Li River
Boat
1 2 2 (in/out)
Guilin
Chengdu
Pandas
2 3 2 (in/out)
Chengdu
Hangzhou 1 1 train
Yangtse Cruise 4
(on boat)
5 2 (in/out)
Chongqing/
Yichang

The above includes a little bit of shopping and relax time, but not much. If you want leisurely pace, add a day in the major stops.

A reminder also, most international flights will arrive in either Beijing or Shanghai airports, so it’s likely one of those will be your first city. Ideally, (but not if you are using a 72 hour transit visa) book your return exit from China from the other city, avoiding another another day and another flight domestically to return you to your starting city.

Recommended Sightseeing Route
China Sightseeing

You can do your own research into details about what to see and do, however, I often given advise to those coming to China to hire a local guide/driver in each city, and try and not miss at least the following.

Beijing Forbidden City

Beijing Forbidden City

Beijing 北京

The Forbidden City, which housed 24 emperors of the Ming and Qing dynasties (1368–1911), is the best preserved imperial palace in China and the largest ancient palatial structure in the world. The design and the layout of the 870 buildings in the palace represent the essence of traditional Chinese architecture.
Time Needed: 1/2 day (fast) 1 day (exhaustion)
Tian’anmen Square is the largest public square, and can accommodate a million people. It is where the ceremony for the founding of the People’s Republic was held.
Time Needed: 1 hour (drive) 3 hours (walk)
The Great Wall of China extends 4,000 miles. Construction of the wall began over 2,000 years ago and lasted for over 1,000 years. There are several Great Wall sections around Beijing, including restored sections and rugged sections. The most famous sections to visit include: Mutianyu, Jinshanling and Jiankou.
Time Needed: 1 day (drive – rental car)
The Beijing hutongs are mazes of narrow alleyways linking old single-story traditional courtyard houses. Hutongs give a wonderful glimpse into the world of yesterday in Beijing. Visiting a hutong family living in a traditional quadrangle dwelling is a nice way to discover traditional Beijing life.
Time Needed: Afternoon & Evening (walk)
Tasting Peking Duck (Beijing roast duck) is the epitome of Beijing cuisine and also one of the eight most popular Chinese dishes. The dish is mostly prized for the thin, crispy skin, with authentic versions of the dish serving mostly the skin and little meat.
Time Needed: 1 evening
Shanghai Pudong Skyline

Shanghai Pudong

Shanghai 上海

Strolling along The Bund is one of the things you should never miss when on a tour to Shanghai. The Bund displays Shanghai’s classic skyline views of colonial architecture and skyscrapers along the 500m wide Huangpu River, which dissects the city into two.
Time Needed: Afternoon & Evening (walk)
A ride in the worlds fastest train (Maglev) from Pudong Airport to the city at 431 kph (270 mph), is twice the speed of a theme park roller coaster. The magnetically-levitated train covers 30 km (19 miles) in only 8 minutes, though you hardly feel you’re moving!
Time Needed: 2 hours
Shanghai Old Street, is an old business street that has 225 tourist shops from the Ming Dynasty (1368-1644) until the period when European influence made an impact on the city. Shops sell handicraft articles, paintings, calligraphies and jewelry. At the western end of the street is where items of folk culture may be bought from ‘antique’ shops, embroidery houses and fabric shops.
Time Needed: 5 hours
Xi'an Bell Tower

Xi’an Bell Tower

Xi’an  西安市

Visit the Terracotta Warriors and Horses which were discovered accidentally in 1974, the Terracotta army of over 7,000 soldiers, horses and chariots in full battle array has been guarding Emperor Qin’s tomb since 210BC.
Time Needed: 2 hours (fast), 1/2 day (full), plus 2 hours drive time.
The Muslim Quarter is a fantastic place to wonder, particularly late afternoon early evening. All shops and restaurants in the street are operated by Muslims. The stalls lines the narrow alleys sell almost everything you can expect.
Time Needed: Afternoon & Evening (walk)